Late on a Saturday evening in San Francisco, at a party filled with tech workers, people keep retreating to odd corners to stare at their phones. This happens at every party these days, of course, but what’s different here is that the partygoers are all staring at, and talking about, an app called Secret. Lately it’s been topic number one among Silicon Valley tech workers, venture capitalists, and the media who cover them. All around San Francisco, people are devouring their Secret feeds, with their unpredictable mix of sex, drugs, and industry gossip. Valentine’s Day threesomes, photos of your best weed, blow jobs in the restaurant kitchen — it’s all here, maybe true and maybe not, but guaranteed to get you guessing about who posted it.